Hello all, Today I'm doing a hiking, its not the 1st time I do that that hike and everytime the resulting gpx is a bit disappointing...

The track is in the side of a big rock (Gibraltar)

alt text

which I suppose it makes it very difficult to get a good gps signal to make things worst today is a bit cloudy...

Can anyone help me setting the best configuration for an precise track logging...

-GPS mode: Normal or WAAS/EGNOS

-Track Log recording Method: Distance / Time or Auto

-Track Log recording Rate: I suppose is the Most often

-Altimeter: should I change anything?


asked 11 Apr '14, 09:54

rsbarbosa's gravatar image

accept rate: 0%

edited 11 Apr '14, 09:55

I would only use the gps to get some calibration traces and then use what appears to be good Bing in that area and map from that. As you say set gps to record once a second and then when you have a large angle of the sky all around and stay still for few minutes so you get a good blob that you can average and pin point on bing. I have vague recollection that the satellite view page (on a Garmin) shows some concentric rings that indicate the angles the satellites are above the horizon which may help you decide if the area in open enough. it's not easy.EDIT Page 5 or 81? of this explains the concentric rings. http://www.rgs.org/NR/rdonlyres/95D99DBD-CE9B-4B89-81F3-22D12B3B976E/0/Chapter6TheGlobalPositioningSystemGPSPrinciplesandConcepts.pdf

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answered 11 Apr '14, 16:05

andy%20mackey's gravatar image

andy mackey
accept rate: 4%

edited 11 Apr '14, 23:37


My Garmin has a waypoint averaging feature. If yours has that then you can leave the GPS on for a while at a point that has good satellite visibility and will be a readily visible point on the Bing imagery. Should give you a reasonable point to align the imagery to trace. Probably want to do that in a couple of places that meet the two criteria of GPS satellite visibility and identifiability on Bing.

(11 Apr '14, 16:50) n76

You'll struggle to get an accurate GPS trace with that big rock in the way! Any satellites the other side of the hill will be hidden.

What you might be able to do is to note down things along the track (as waypoints, or some other sort of timed notes) that allows you to correlate your GPS track with aerial imagery (and if you can get a second source of imagery to mitigate against imagery offset, so much the better).

Whether EGNOS will help you in Gibraltar I'm not sure. Measure a few tracks with and without it and compare. In England an eTrex gives significantly better traces with WAAS/EGNOS turned on rather than off, but people have reported issues elsewhere.

I'd be surprised if the altimeter has an effect on the horizontal position of a logged GPX point (you'd probably need someone with a Dakota to comment on that though).

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answered 11 Apr '14, 10:10

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 15%


Callibrating the altimeter (if you're at a known altitude) and the compas is usefull but not really for osm purposes.

WAAS/EGNOS might pointlessly use more power, but shouldn't make positioning worse.

The only thing that might make a difference on the side of a cliff is Glonass, but even then it probably won't be much. I once carried both a dakota20 and a gpsmap62s in tricky urban terrain; the 62s fared slightly better but not by much.

(14 Apr '14, 11:15) Vincent de P... ♦
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question asked: 11 Apr '14, 09:54

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last updated: 14 Apr '14, 11:15

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